sensecap solar: add poweroff/shutdown support and nrf52 PM parity

[Specter242]

Summary

Add SenseCAP Solar repeater power-management parity for software shutdown:

• Add board-level power management hooks for SenseCAP Solar (initiateShutdown, powerOff) with button-based wake/system-off behavior.
• Enable required SenseCAP Solar variant defines for NRF52 power-management.
• Add SenseCAP Solar LED/wiring parity updates:
  • update LoRa TX LED pin mapping (P_LORA_TX_LED) from 12 to 11 for board wiring parity,
  • explicitly switch LED_GREEN and LED_BLUE off in powerOff() before entering system-off.
• Add CLI aliases: poweroff and shutdown.
• Add stability/usability fixes for real device behavior:
  • configure wake button with pull-up in system-off to avoid floating/false wake,
  • add SenseCAP Solar repeater long-press user-button shutdown (hold ~1.5s).
• Update NRF52 power-management support docs matrix for SenseCAP Solar.

Why

SenseCAP Solar repeater firmware lacked a practical software power-off path and CLI shutdown command. This improves battery-device operability and aligns behavior with expected NRF52 power-management support.

Fixes #1872
Related to #1145

Validation

• ~/.local/bin/pio run -e SenseCap_Solar_repeater (SUCCESS)
• Verified firmware links and artifacts are produced for the target environment.